// CopyBytesToJS copies bytes from src to dst.
// It panics if dst is not a Uint8Array or Uint8ClampedArray.
// It returns the number of bytes copied, which will be the minimum of the lengths of src and dst.
func CopyBytesToJS(dst Value, src []byte) int {
	n, ok := copyBytesToJS(dst.ref, src)
	runtime.KeepAlive(dst)
	if !ok {

		if err != nil {
			req.Body.Close() // RoundTrip must always close the body, including on errors.
			return nil, err
		}
		req.Body.Close()
		if len(body) != 0 {
			buf := uint8Array.New(len(body))
			js.CopyBytesToJS(buf, body)
			opt.Set("body", buf)
		}
	}

	fetchPromise := js.Global().Call("fetch", req.URL.String(), opt)
	var (
		respCh           = make(chan *Response, 1)
		errCh            = make(chan error, 1)

			src := make([]byte, tt.srcLen)
			if tt.srcLen >= 2 {
				src[1] = 42
			}
			dst := js.Global().Get("Uint8Array").New(tt.dstLen)

			if got, want := js.CopyBytesToJS(dst, src), tt.copyLen; got != want {
				t.Errorf("copied %d, want %d", got, want)
			}
			if tt.dstLen >= 2 {
				if got, want := dst.Index(1).Int(), 42; got != want {
					t.Errorf("got %d, want %d", got, want)